1. Field of the Invention
This invention relates to adhesive compositions which adhere strongly to any of the hard tissues of the living body, such as teeth and bones, metal materials, organic polymer materials and ceramic materials and are excellent in water resistance of adhesive strength. The term "adhesive compositions" as herein used not only means compositions used for bonding a plurality of adherends to one another, but also covers compositions used for forming highly adhesive coatings on the surfaces of adherends such as metal materials, organic polymer materials, etc. and compositions used for forming highly adhesive filling materials for repairing hard tissues of the living body. In other words, the adhesive compositions of this invention comprehend all the compositions which exhibit adhesion to and thus are applicable to various kinds of substances, such as hard tissues of the living body, metal materials, organic polymer materials, ceramic materials, etc.
2. Description of the Prior Art
Various kinds of metal materials, organic polymer materials and ceramic materials are used for the restoration of teeth. When these restorative materials are mounted in the mouth, it is necessary to ensure the adhesion between the teeth and the metal, organic polymer or ceramic material, and also the adhesion of the restorative materials to each other, for example, metal to metal, ceramics or organic polymer. In particular, since they are used in the mouth in the dentistry field, it is required that the adhesion be satisfactory under wet conditions.
Heretofore, a variety of attempts to use phosphate compounds in adhesive compositions have been made widely in the dentistry field.
(1) U.S. Pat. Nos. 4,259,075, 4,259,117 and 4,368,043 describe that a polymerizable composition containing a vinyl compound having a group of the formula: ##STR2## is effective as a dental adhesive. U.S. Pat. No. 4,222,780 describes that a polymerizable composition containing a vinyl compound having a group of the formula: ##STR3## is also an effective dental adhesive. In fact, some of the compositions falling within the scopes of the above patents have been materialized and widely employed as primers for coating the cavity wall before the tooth cavity is filled. However, they had a problem in that the cavity wall must be acid etched beforehand in order to provide satisfactory adhesive strength to the tooth and also another problem in that they do not have satisfactory adhesive strength to a Ni--Cr alloy commonly employed in dentistry.
(2) Attempts to obtain adhesives having adhesion to tooth using polymerizable phosphate compounds have also been made and examples thereof include the following:
(i) U.S. Pat. No. 3,882,600 describes phosphoryl monofluoride.
(ii) Journal of Dental Research, vol. 53, p. 878-888 and vol. 56, p. 943-952, Chemical Abstract, vol. 77, p. 290 (66175 g) and Japanese Patent Application Laid-open No. 44152/1976 describe CH.sub.2 .dbd.CH--PO(OH).sub.2 and CH.sub.2 .dbd.CHC.sub.6 H.sub.4 CH.sub.2 PO(OH).sub.2. (iii) Japanese Patent Application Laid-open No. 113843/1978 shows compounds, by a general formula, which are obtained by neutralizing one of the two hydroxyl groups in compounds of the formula: ##STR4## wherein R represents an organic residue having at least one vinyl group, and specific examples thereof include the following (wherein M represents an alkali metal): ##STR5##
(iv) Japanese Patent Publication No. 49557/1982 describes methacryloyloxyethane-1,1-diphosphonic acid of the following formula: ##STR6## as an adhesive component in a dental adhesive.
In every case of the compounds described in (i) to (iv) above, high adhesive strength (especially to metals) under wet conditions cannot be obtained.
(3) Examples of other attempts to obtain adhesive compositions having adhesion to both teeth and metals include the following:
(i) U.S. Pat. No. 4,148,988 shows 4-methacryloxyethyl trimellitate as an adhesive monomer. This monomer, however, cannot maintain a strong bond between the tooth and a metal or organic polymer material for a prolonged time in the mouth which is under wet conditions and moreover under repeated occlusal pressure.
(ii) U.S. Pat. No. 3,872,047 and Japanese Patent Application Laid-open No. 98878/1974 disclose a polymer having both a hydrophilic group and a hydrophobic group as an adhesive component. As the monomer constituting said polymer, they disclose methacryloxyethyl phosphate, etc., but their adhesive strength seems inadequate.
(iii) It is known that a polymer obtained by polymerizing a vinyl monomer on the tooth surface by employing a ternary curing agent consisting of a peroxide, an amine and a sulfinic acid salt improves the adhesive strength to the tooth (U.S. Pat. No. 4,182,035). However, no satisfactory adhesive strength can be obtained by a combination with any conventional vinyl monomer, and thus it is necessary to explore a new adhesive vinyl monomer for this purpose.
(4) Further, attempts to employ phosphate compounds in adhesive compositions have been made widely in various industries. Examples thereof are disclosed in U.S. Pat. Nos. 3,754,972, 3,884,864, 3,987,127, 4,001,150, 4,044,044, 4,223,115; Japanese Patent Application Laid-open Nos. 20238/1974; 100596/1975, 125182/1976, 12995/1978, 11920/1981, 44638/1982, Japanese Patent Publication Nos. 4126/1980; 4790/1980, etc. However, none of these phosphate compounds described in the above patent literature are free from a problem associated with water resistance of adhesive strength.